If you're looking for the power of customization, and security.. check out the Drupal Project. drupal.org
As a Webhost Technician I can't begin to tell you how many clients submit tickets because their Joomla, or Wordpress installations were hacked due to lack of upgrading and keeping their security tight in their custom mods.
The bigger well known CMS sites become targets for hackers. This is so if they find a exploit that have a huge list to drop their root kits, or cause other malicious activities on your account. I had someone submit a ticket on my last shift. He lost over 2 years of articles because he never upgraded in two years, and didn't do any cPanel back ups. Our back up's are only use are only for complete hardware failure only going back 3-4 days. He was compromised 3-4 weeks prior before he noticed and lost everything to a script kittie
